Commit | Line | Data |
---|---|---|
f1b2fa5b | 1 | /* tcp_output.c 4.20 81/11/29 */ |
76ee76df BJ |
2 | |
3 | #include "../h/param.h" | |
4 | #include "../h/systm.h" | |
5 | #include "../h/mbuf.h" | |
6 | #include "../h/socket.h" | |
d52566dd | 7 | #include "../h/socketvar.h" |
0974b45c BJ |
8 | #include "../net/in.h" |
9 | #include "../net/in_pcb.h" | |
10 | #include "../net/in_systm.h" | |
d52566dd | 11 | #include "../net/ip.h" |
eb44bfb2 | 12 | #include "../net/ip_var.h" |
d52566dd | 13 | #include "../net/tcp.h" |
0974b45c | 14 | #define TCPOUTFLAGS |
d52566dd | 15 | #include "../net/tcp_fsm.h" |
0974b45c BJ |
16 | #include "../net/tcp_seq.h" |
17 | #include "../net/tcp_timer.h" | |
18 | #include "../net/tcp_var.h" | |
19 | #include "../net/tcpip.h" | |
f1b2fa5b | 20 | #include "../errno.h" |
76ee76df | 21 | |
ea727f86 | 22 | /* |
a6503abf BJ |
23 | * Tcp output routine: figure out what should be sent |
24 | * and, if nothing, send a null segment anyways if force is nonzero | |
25 | * (e.g. to be sure to send an ACK). | |
26 | * | |
27 | * This routine can be called only after SYNs have been exchanged. | |
ea727f86 | 28 | */ |
a6503abf | 29 | tcp_output(tp) |
53a5409e | 30 | register struct tcpcb *tp; |
ea727f86 | 31 | { |
53a5409e | 32 | register struct socket *so = tp->t_inpcb->inp_socket; |
a6503abf BJ |
33 | register int len; |
34 | struct mbuf *m0; | |
35 | int off, flags; | |
36 | register struct mbuf *m; | |
37 | register struct tcpiphdr *ti; | |
38 | int win; | |
76ee76df | 39 | |
a6503abf | 40 | COUNT(TCP_OUTPUT); |
76ee76df | 41 | |
a6503abf | 42 | /* |
0974b45c BJ |
43 | * Determine length of data that can be transmitted, |
44 | * and flags that will be used. | |
45 | * If there is some data or critical controls (SYN, RST) | |
46 | * to send, then transmit; otherwise, investigate further. | |
a6503abf BJ |
47 | */ |
48 | off = tp->snd_nxt - tp->snd_una; | |
49 | len = MIN(so->so_snd.sb_cc, tp->snd_wnd) - off; | |
0974b45c BJ |
50 | if (len > tp->t_maxseg) |
51 | len = tp->t_maxseg; | |
52 | flags = tcp_outflags[tp->t_state]; | |
53 | if (len || (flags & (TH_SYN|TH_RST))) | |
a6503abf BJ |
54 | goto send; |
55 | ||
56 | /* | |
0974b45c | 57 | * See if we owe peer an ACK or have a unacked FIN to send. |
a6503abf | 58 | */ |
0974b45c | 59 | if (tp->t_flags & TF_ACKNOW) |
a6503abf | 60 | goto send; |
0974b45c BJ |
61 | if ((so->so_state & SS_CANTSENDMORE) && |
62 | TCPS_OURFINNOTACKED(tp->t_state)) | |
a6503abf | 63 | goto send; |
76ee76df | 64 | |
a6503abf BJ |
65 | /* |
66 | * Calculate available window in i, and also amount | |
67 | * of window known to peer (as advertised window less | |
68 | * next expected input.) If this is 35% or more of the | |
69 | * maximum possible window, then want to send a segment to peer. | |
70 | */ | |
0974b45c BJ |
71 | win = sbspace(&so->so_rcv); |
72 | if (win > 0 && | |
73 | ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35)) | |
a6503abf BJ |
74 | goto send; |
75 | ||
76 | /* | |
77 | * No reason to send a segment, just return. | |
78 | */ | |
f1b2fa5b | 79 | return (0); |
a6503abf BJ |
80 | |
81 | send: | |
82 | /* | |
83 | * Grab a header mbuf, attaching a copy of data to | |
84 | * be transmitted, and initialize the header from | |
85 | * the template for sends on this connection. | |
86 | */ | |
76ee76df BJ |
87 | MGET(m, 0); |
88 | if (m == 0) | |
89 | return (0); | |
53a5409e BJ |
90 | m->m_off = MMAXOFF - sizeof(struct tcpiphdr); |
91 | m->m_len = sizeof (struct tcpiphdr); | |
a6503abf BJ |
92 | if (len) { |
93 | m->m_next = m_copy(so->so_snd.sb_mb, off, len); | |
94 | if (m->m_next == 0) | |
95 | len = 0; | |
96 | } | |
97 | ti = mtod(m, struct tcpiphdr *); | |
98 | if (tp->t_template == 0) | |
99 | panic("tcp_output"); | |
f1b2fa5b | 100 | bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr)); |
a6503abf BJ |
101 | |
102 | /* | |
103 | * Fill in fields, remembering maximum advertised | |
104 | * window for use in delaying messages about window sizes. | |
105 | */ | |
106 | ti->ti_seq = htonl(tp->snd_nxt); | |
0974b45c BJ |
107 | ti->ti_ack = htonl(tp->rcv_nxt); |
108 | if (tp->t_tcpopt) { | |
f1b2fa5b | 109 | m0 = m->m_next; |
0974b45c BJ |
110 | m->m_next = m_get(0); |
111 | if (m->m_next == 0) { | |
112 | (void) m_free(m); | |
f1b2fa5b | 113 | m_freem(m); |
0974b45c BJ |
114 | return (0); |
115 | } | |
116 | m->m_next->m_next = m0; | |
117 | m->m_off = MMINOFF; | |
118 | m->m_len = tp->t_tcpopt->m_len; | |
119 | bcopy(mtod(tp->t_tcpopt, caddr_t), mtod(m, caddr_t), | |
f1b2fa5b | 120 | (unsigned)tp->t_tcpopt->m_len); |
0974b45c BJ |
121 | ti->ti_off = (sizeof (struct tcphdr)+tp->t_tcpopt->m_len) >> 2; |
122 | } | |
123 | ti->ti_flags = flags; | |
a6503abf BJ |
124 | win = sbspace(&so->so_rcv); |
125 | if (win > 0) | |
f1b2fa5b | 126 | ti->ti_win = htons((u_short)win); |
0974b45c BJ |
127 | if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { |
128 | ti->ti_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); | |
a6503abf BJ |
129 | ti->ti_flags |= TH_URG; |
130 | } else | |
131 | /* | |
132 | * If no urgent pointer to send, then we pull | |
133 | * the urgent pointer to the left edge of the send window | |
134 | * so that it doesn't drift into the send window on sequence | |
135 | * number wraparound. | |
136 | */ | |
0974b45c BJ |
137 | tp->snd_up = tp->snd_una; /* drag it along */ |
138 | /* PUSH */ | |
a6503abf BJ |
139 | |
140 | /* | |
141 | * Put TCP length in extended header, and then | |
142 | * checksum extended header and data. | |
143 | */ | |
144 | if (len) | |
145 | ti->ti_len = htons((u_short)(len + sizeof (struct tcphdr))); | |
0974b45c BJ |
146 | ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + len); |
147 | ||
148 | /* | |
149 | * Advance snd_nxt over sequence space of this segment | |
150 | */ | |
151 | if (flags & (TH_SYN|TH_FIN)) | |
152 | len++; | |
153 | tp->snd_nxt += len; | |
154 | ||
155 | /* | |
156 | * Arrange for retransmit and time this transmit if | |
157 | * not already a retransmit and sending either data, | |
158 | * SYN or FIN. | |
159 | */ | |
160 | if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { | |
161 | tp->rxt_seq = tp->snd_nxt - len; | |
162 | tp->rxt_time = 0; | |
163 | tp->rxt_cnt = 0; | |
164 | tp->t_timer[TCPT_REXMT] = 0; /* XXX */ | |
165 | } | |
a6503abf BJ |
166 | |
167 | /* | |
168 | * Fill in IP length and desired time to live and | |
169 | * send to IP level. | |
170 | */ | |
171 | ((struct ip *)ti)->ip_len = len + sizeof (struct tcpiphdr); | |
172 | ((struct ip *)ti)->ip_ttl = TCP_TTL; | |
0974b45c BJ |
173 | if (ip_output(m, tp->t_ipopt) == 0) |
174 | return (0); | |
a6503abf BJ |
175 | |
176 | /* | |
177 | * Data sent (as far as we can tell). | |
178 | * If this advertises a larger window than any other segment, | |
179 | * then record its sequence to be used in suppressing messages. | |
0974b45c | 180 | * Drop send for purpose of ACK requirements. |
a6503abf BJ |
181 | */ |
182 | if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) | |
183 | tp->rcv_adv = tp->rcv_nxt + win; | |
0974b45c BJ |
184 | tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); |
185 | tp->snd_max = tp->snd_nxt; | |
186 | return (1); | |
76ee76df | 187 | } |